Tilt-up (or precast) construction of concrete wall sections is well-known in the art. In such an approach, forms are placed edgewise on a flat casting surface, and filled with concrete, which is then cured. Once the concrete has set, the form is removed and the wall is tilted up into the preferred, typically vertical, orientation. Most forms are made of conventional wood planks, such as two-by-eights and the like. To keep the forms from shifting during the form assembly portion of the operation, as well as to provide smooth, beveled edges to the finished concrete slab, single or double chamfers have been employed. These chamfers are often in the shape of a triangle with an extended base for plank edge support (in the case of the single chamfer variant), or a trapezoidal member with a plank-engaging channel disposed in the center (the dual chamfer variant). When placed in the chamfer, the vertically extending widthwise dimension of the plank defines the thickness of the concrete wall panel to be poured. The chamfer is placed to engage every plank that makes up the form.
One problem associated with conventional chamfer construction is the tendency of the poured concrete to leak into gaps prior to drying and hardening. This problem is especially acute between the chamfer and the casting surface, and between the chamfer and the plank, as the resulting dried portion that has leaked through can stick to the chamfer, which can in turn lead to an unintended, cost-prohibitive one-time chamfer use. In addition, if the dried concrete that has leaked through bonds to the finished product wall section and subsequently breaks off during handling, the bond might be strong enough to take portions of the finished product with it, thus adversely effecting the quality of the finished product. Prior art attempts at providing a seal to preclude the occurrence of leaking have been of a passive nature in that the chamfer relies on a close fit to accept a plank of standard thickness without gaps, but does nothing to actively close plank-to-chamfer gaps. In addition, no attempts have been made to provide seals between the chamfer and the casting surface.
Accordingly, there exists a need for a device that can ensure that tilt-up wall panels are precast with a minimum amount of poured concrete bleed-through, thereby avoiding frame-chamfer bonding and subsequent difficulty in separating the two.